Passively Q-switched nanosecond pulse-train Nd:YAG laser system

In our experiment number of laser pulses in the laser pulse train was controlled by changing of the oscillator flashlamp
pumping energy for 1 ms duration of the flashlamp pulse to matched with lifetime of the gas puff target. The number of
laser pulses as a function of flashlamp pumping energy is shown in Fig. 5.
Q)Cl)
• E
0,4
0,2
0,0
200
400
600
800
1000
Fig. 5. Laser pulse trains as a function of oscillator pumping energy.
The laser pulses creating trains shown in Fig. 5 have equal energy and duration (FWHM). Laser pulse train energy vs.
number of laser pulses is shown in Fig. 6.
30
25
20
E 15
a)
w 10
2 4 6 8 10
15
Number of pulses
Fig. 6. Energy ofthe laser pulse train vs. number of pulses.
Low intensity laser pulses from the oscillator should be amplified to obtain intensity required for effective EUV and soft
X-ray production (101 1.4013 W/cm2). Assuming 100 tm diameter of the focus we should have 100 mJ of energy for 1 3 ns
laser pulse to reach power density of lOl 1W/cm2 after focusing of the laser beam. To obtain a flat envelope of the
amplified laser pulse train the energy of a single laser pulse should be chosen in such a way, that depletion of the
inversion caused by the passage of the one pulse will be equal to the production of the inversion between two pulses.
Then the inversion will be constant during a pulse train and each pulse will experience the same gain. For fixed oscillator
20
25
30
35
Proc. of SPIE Vol. 5707 351